U.S. patent number 10,435,566 [Application Number 15/537,516] was granted by the patent office on 2019-10-08 for particles for electrophoretic displays.
This patent grant is currently assigned to Merck Patent GmbH. The grantee listed for this patent is Merck Patent GmbH. Invention is credited to Louise Diane Farrand, Mark John Goulding, Mark James, Christopher Lutz, Nathan Smith, Jonathan Henry Wilson.
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United States Patent |
10,435,566 |
Farrand , et al. |
October 8, 2019 |
Particles for electrophoretic displays
Abstract
This invention relates to polymer particles preferably with
surface functionality for charge retention, a process for their
preparation, the use of these particles for the preparation of an
electrophoretic device, electrophoretic displays comprising such
particle, and new polymerizable dyes.
Inventors: |
Farrand; Louise Diane (Dorset,
GB), Wilson; Jonathan Henry (Darmstadt,
DE), James; Mark (Romsey, GB), Lutz;
Christopher (Hassenroth, DE), Smith; Nathan
(Southampton, GB), Goulding; Mark John (Ringwood,
GB) |
Applicant: |
Name |
City |
State |
Country |
Type |
Merck Patent GmbH |
Darmstadt |
N/A |
DE |
|
|
Assignee: |
Merck Patent GmbH (Darmstadt,
DE)
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Family
ID: |
52144365 |
Appl.
No.: |
15/537,516 |
Filed: |
November 27, 2015 |
PCT
Filed: |
November 27, 2015 |
PCT No.: |
PCT/EP2015/002392 |
371(c)(1),(2),(4) Date: |
June 19, 2017 |
PCT
Pub. No.: |
WO2016/096091 |
PCT
Pub. Date: |
June 23, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180037744 A1 |
Feb 8, 2018 |
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Foreign Application Priority Data
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Dec 19, 2014 [EP] |
|
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14004338 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07D
285/08 (20130101); C08F 220/14 (20130101); C07D
265/34 (20130101); C09B 69/106 (20130101); G02F
1/167 (20130101); C07D 277/82 (20130101); C09B
62/008 (20130101); C09B 69/109 (20130101); C09B
69/101 (20130101); C08F 293/00 (20130101); G02F
2001/1678 (20130101); G02F 2202/022 (20130101) |
Current International
Class: |
C08F
220/14 (20060101); C09B 62/008 (20060101); C07D
265/34 (20060101); C07D 277/82 (20060101); C09B
69/10 (20060101); C07D 285/08 (20060101); G02F
1/167 (20190101); C08F 293/00 (20060101); G02F
1/1675 (20190101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1491941 |
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Dec 2004 |
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EP |
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2438436 |
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Nov 2007 |
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GB |
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WO-9910767 |
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Mar 1999 |
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WO |
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WO-2005017046 |
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Feb 2005 |
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WO |
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WO-2006126120 |
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Nov 2006 |
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WO |
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WO-2007048721 |
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May 2007 |
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WO |
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WO-2008003604 |
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Jan 2008 |
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WO |
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WO-2008003619 |
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Jan 2008 |
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WO |
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WO-2010087841 |
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Aug 2010 |
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WO |
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WO-2010089057 |
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Aug 2010 |
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WO |
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WO-2010089060 |
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Aug 2010 |
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WO |
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WO-2012019704 |
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Feb 2012 |
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WO |
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WO-2013079146 |
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Jun 2013 |
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WO |
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WO-2013170935 |
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Nov 2013 |
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WO |
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WO-2014166583 |
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Oct 2014 |
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WO |
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Other References
Blunden et al. Biomacromolucues Nov. 2013 pp. 4177-4188 (Year:
2013). cited by examiner .
Bouhadir, G., et al., "A New Practical Synthesis of Tertiary
S-Alkyl Dithiocarbonates and Related Derivatives", Tetrahedron
Letters, vol. 40, No. 2, (1999), pp. 277-280. cited by applicant
.
Chiefari, J., et al., "Living Free-Radical Polymerization by
Reversible Addition--Fragmentation Chain Transfer: The RAFT
Process", Macromolecules, vol. 31, No. 16, (1998), pp. 5559-5562.
cited by applicant .
International Search Report for PCT/EP2015/002392 dated Mar. 11,
2016. cited by applicant .
Kim, T.H., et al., "Preparation and Characterization of Colored
Electronic Ink Nanoparticles by High Temperature-Assisted Dyeing
for Electrophoretic Displays", Journal of Nanoscience and
Nanotechnology, vol. 6, No. 11, (2006), pp. 3450-3454. cited by
applicant .
Moad, G., et al., "Living free radical polymerization with
reversible addition--fragmentation chain transfer (the life of
RAFT)", Polymer International, vol. 49, No. 9, (2000), pp.
993-1001. cited by applicant .
Thang, S., et al., "A Novel Synthesis of Functional Dithioesters,
Dithiocarbamates, Xanthates and Trithiocarbonates", Tetrahedron
Letters, vol. 40, No. 12, (1999), pp. 2435-2438. cited by applicant
.
Written Opinion of the International Searching Authority for
PCT/EP2015/002392 dated Mar. 11, 2016. cited by applicant.
|
Primary Examiner: Kaucher; Mark S
Attorney, Agent or Firm: Drinker Biddle & Reath LLP
Claims
The invention claimed is:
1. A coloured polymer particle for use in electrophoretic devices
comprising at least one A-B diblock copolymer comprising a
hydrophobic polymer block A and a hydrophilic polymer block B
containing a charge or being chargeable, and monomer units of at
least one monomer, of at least one polymerisable dye, optionally of
at least one charged co-monomer, and optionally of at least one
crosslinking co-monomer, wherein the A-B diblock copolymer consists
of PMMA as block A and PDMAEMA as block B.
2. The coloured polymer particle according to claim 1, wherein
diblock copolymer is a PMMAm-qxPDMAEMAn wherein m is the number of
monomer units of block A and m is >10, n is the number of
monomer units of block B and n is >10, and qx is the percentage
of quaternisation of block B based on the total number of amino
groups and qx is >10%.
3. The coloured polymer particle according to claim 2, wherein m is
in the range of 15-110, n is in the range of 10-20, and qx is 10%,
20% or 100%.
4. The coloured polymer particle according to claim 1, wherein
block B is charged with 0.2% to 100% permanent charge based on
partially or completely quaternised nitrogen groups.
5. The coloured polymer particle according to claim 1, wherein a
polymerisable dye comprises a chromophore, at least one
polymerisable group, optionally at least one linker group, and
optionally at least one charged group is used.
6. The coloured polymer particle according to claim 1, wherein the
polymer particles have a diameter of 50-1000 nm.
7. The coloured polymer particle according to claim 1, wherein a
water-soluble polymerisable dye is used.
8. The coloured polymer particle according to claim 1, wherein a
water-soluble polymerisable dye is used selected from Disperse Red
1 methacrylate or acrylate, a dye of Formula 1, a dye of Formula 2,
a dye of formula 3, a dye of formula 4, a dye of formula 5a/b, or a
dye of formula 6a/b, and a dye of Formula 7 ##STR00063##
##STR00064## wherein R1, R2, R3, R5, R7 are alkyl, R4, R6, R8 are H
or CH.sub.3, Hal=halogen, R9, R10, R12, R13, R15, and R17 to R19=H
and alkyl, R11, R14, R16, and R20=H or CH.sub.3, L is a single
bond, optionally substituted cycloalkyl or aromatic ring, linear or
branched, optionally substituted, alkylene, where one or more
non-adjacent C atoms may be replaced by O, S and/or N, and/or one
or more double and/or triple bonds may be present in the chain
and/or side chain or a combination thereof, and A.sup.-=halogen,
monobasic acid (oxo) anions.
9. A process for the preparation of coloured polymer particles for
use in electrophoretic devices, comprising a) the reaction of at
least one monomer, at least one A-B diblock copolymer consisting of
PMMA as block A and PDMAEMA as block B at least one initiator,
optionally at least one polymerisable dye, optionally of at least
one charged co-monomer, and optionally of at least one crosslinking
co-monomer, b) optionally colouring the polymer particles by
incorporation of at least one dye and/or at least one
pre-polymerised dye and/or at least one polymerisable dye, and
optionally c) washing the polymer particles.
10. The process according to claim 9, wherein the A-B diblock
copolymer is a PMMAm-qxPDMAEMAn, wherein m is the number of monomer
units of block A and m is >10, n is the number of monomer units
of block B and n is >10, and qx is the percentage of
quaternisation of block B based on the total number of amino groups
and qx is >10%.
11. The process according to claim 9, wherein block B is charged
with 0.2% to 100% permanent charge based on partially or completely
quaternised nitrogen groups.
12. The process according to claim 9, wherein a water-soluble
polymerisable dye is used in step a) or b), a dye of Formula 1, a
dye of Formula 2, a dye of formula 3, a dye of formula 4, a dye of
formula 5a/b, or a dye of formula 6a/b, and a dye of Formula 7
##STR00065## ##STR00066## wherein R1, R2, R3, R5, R7=alkyl, R4, R6,
R8=H or CH.sub.3, Hal=halogen, R9, R10, R12, R13, R15, and R17 to
R19=H and alkyl, R11, R14, R16, and R20=H or CH.sub.3, L is a
single bond, optionally substituted cycloalkyl or aromatic ring,
linear or branched, optionally substituted, alkylene, where one or
more non-adjacent C atoms may be replaced by O, S and/or N, and/or
one or more double and/or triple bonds may be present in the chain
and/or side chain or a combination thereof, and A.sup.-=halogen,
monobasic acid (oxo) anions.
13. The process according to claim 9, wherein the polymer particles
are prepared from a composition comprising a monomer, a A-B block
copolymer, a crosslinker, polymerisable dye, an ionic co-monomer,
and an initiator in a batch emulsion process.
14. A method comprising utilizing the polymer particles according
to claim 1 in optical, electrooptical, electronic, electrochemical,
electrophotographic, electrowetting and electrophoretic displays
and/or devices, and in security, cosmetic, decorative, and
diagnostic applications.
15. An electrophoretic fluid comprising polymer particles according
to claim 1.
16. An electrophoretic display device comprising electrophoretic
fluid according to claim 15.
17. The electrophoretic display device according to claim 16,
wherein the electrophoretic fluid is applied by a technique
selected from inkjet printing, slot die spraying, nozzle spraying,
and flexographic printing, or any other contact or contactless
printing or deposition technique.
18. The coloured polymer particle according to claim 1, wherein the
A-B diblock copolymer is selected from PMMA.sub.14-PDMAEMA.sub.21,
PMMA.sub.14-q.sub.20PDMAEMA.sub.21,
PMMA.sub.14-q.sub.100PDMAEMA.sub.21, PMMA.sub.14-PDMAEMA.sub.54,
PMMA.sub.14-q.sub.20PDMAEMA.sub.54,
PMMA.sub.14-q.sub.100PDMAEMA.sub.54, PMMA.sub.14-PDMAEMA.sub.108,
PMMA.sub.14-q.sub.20PDMAEMA.sub.108, PMMA.sub.14-q.sub.100 and
PDMAEMA.sub.108.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a national stage application (under 35 U.S.C.
.sctn. 371) of PCT/EP2015/002392, filed Nov. 27, 2015, which claims
benefit of European Application No. 14004338.1, filed Dec. 19,
2014, both of which are incorporated herein by reference in their
entirety.
This invention relates to coloured polymer particles, a process for
their preparation, the use of these particles for the preparation
of an electrophoretic device, colour electrophoretic displays
comprising such particles, and new polymerisable dyes.
BACKGROUND OF THE INVENTION
In recent years a need has developed for low power, low cost and
light weight display devices. EPDs (Electrophoretic Displays) can
fulfil this requirement. One use of EPDs is for electronic paper.
It is imperative that once an image is displayed, the image can be
retained for a long period of time without further voltage being
applied. Hence, this fulfils the requirements of low power use, and
means an image can be visible until another image is required.
An EPD generally comprises charged electrophoretic particles
dispersed between two substrates, each comprising one or more
electrodes. The space between the electrodes is filled with a
dispersion medium which may be a different colour to the colour of
the particles. The space between the electrodes may also be filled
with a transparent dispersion medium and two kinds of particles
with charge of opposite signs. If a voltage is applied between the
electrodes, charged particles move to the electrode of opposite
polarity. The particles can cover the observer's side electrode, so
that a colour identical to the colour of the particles is displayed
when an image is observed from the observer's side. Any image can
be observed using a multiplicity of pixels. Available technologies
of EPDs include electronic paper, commercially used in electronic
books. This application uses black and white or colour. However,
the main disadvantage of state of the art EPDs is the lack of a
bright full colour system.
The use of different coloured particles in a single pixel has been
exemplified in recent patent literature (U.S. Pat. No. 7,304,634,
GB 2 438 436, US 2007/0268244), but all of these approaches require
the use of complex cell structures and drive schemes. Special
coloured particles for EPDs and processes for their preparation are
disclosed in US 2007/0297038, US 2008/0013156, U.S. Pat. No.
6,822,782, WO 2007/048721, WO 2008/003619, WO 2008/003604, US
2005/0267263, WO 2006/126120, and J. Nanosci. Nanotechn. 2006, Vol.
6, No. 11, p. 3450-3454. Two particle system comprising inorganic
and resin particles are also known (EP 1 491 941). These coloured
particles are only achievable by complicated processes and/or they
are only suitable for specific applications. Similar coloured
particles and their preparation processes are known for analytical
techniques (U.S. Pat. Nos. 5,607,864 and 5,716,855) and as toner
particles for ink jet printing (U.S. Pat. No. 4,613,559).
In EPD, in order to move particles effectively in a non-polar
fluid, and to avoid flocculation of particles, the particles
require to be sterically stabilised and charged. Reported methods
of preparing polymeric particles suitable for EPD are complicated
and have numerous steps. There is a need to simplify the
complicated preparation of polymeric particles suitable for EPD a
simple preparation of charged coloured particles which can be
easily dispersed in non-polar media, show electrophoretic mobility
and which do not leach colour in a dispersant. Therefore, the
object of this invention is to provide electro-optically active
media for colour electrophoretic displays and specifically
engineered coloured particles for use in such media.
This object is solved by polymer particles for use in
electrophoretic devices comprising at least one A-B diblock
copolymer comprising a hydrophobic polymer block A and a
hydrophilic polymer block B containing a charge or being
chargeable, and monomer units of at least one monomer, of at least
one polymerisable dye, optionally of at least one charged
co-monomer, and optionally of at least one cross-linking
co-monomer, by a process for the preparation of polymer particles
for use in electrophoretic devices, comprising a) the reaction of
at least one monomer, at least one A-B diblock copolymer, at least
one initiator, optionally at least one polymerisable dye,
optionally at least one charged co-monomer, and optionally at least
one cross-linking co-monomer, b) optionally colouring the polymer
particles by incorporation of at least one dye and/or at least one
pre-polymerised dye and/or at least one polymerisable dye, and
optionally c) washing the polymer particles, by these particles per
se, by the use of these particles for the preparation of an
electrophoretic device, by electrophoretic displays comprising such
particles, and new polymerisable dyes.
BRIEF SUMMARY OF THE INVENTION
The subject matter of this invention relates specifically to the
use of specifically engineered polymer particles and their
dispersion in dielectric organic media to produce a composition
preferably suitable as the electrically switchable component,
especially of a full colour e-paper or electrophoretic display.
Advantages of the polymer particles according to the invention may
be, in particular: excellent control of particle size, monodisperse
size distribution with a small diameter range of 50-500 nm,
preferably 150-400 nm, for image quality, and/or a glassy polymer
nature for optical clarity and colour compatibility, and/or a
homogeneous crosslinked network structure for solvent resistance,
and/or a non-swelling nature when dispersed in EPD solvent media,
impact strength, hardness, and/or dispersible in a non polar
continuous phase that is the most used media for EPD, and/or high
electrophoretic mobility in dielectric media, and/or technique is
universally applicable for dye incorporation across all colours,
and/or accurate zeta potential is possible, and/or all colours have
same density (good for sedimentation/agglomeration performance),
and/or excellent switching behaviour, faster response times at
comparable voltages, and/or consistent surface properties, and/or
good reproducibility, and/or densities close to that of the carrier
fluid.
The main advantages of the present invention are that it is
possible to prepare particles of appropriate colours e.g. red,
green and blue or a combination of cyan, magenta and yellow and
black, and to be able to prepare coloured particles of a desired
size and which have a high mono-dispersity, which have steric
stability, and preferably incorporate a charge, to enable
electrophoretic movement.
Usually, a monomer composition according to the invention comprises
at least one monomer, at least one A-B diblock copolymer, at least
one initiator, optionally at least one polymerisable dye,
optionally at least one charged co-monomer, and optionally at least
one cross-linking co-monomer. Preferably, a monomer composition
according to the invention comprises a monomer providing the basic
structure, an A-B diblock copolymer, a polymerisable dye, a
cross-linking co-monomer, an ionic co-monomer, and an initiator.
Preferably the polymerisation according to the invention is a free
radical polymerisation. Ionic polymerisation is also
applicable.
DETAILED DESCRIPTION OF THE INVENTION
It is especially preferable to prepare the coloured polymer
particles of the invention in a simple 1-step reaction enabling a
cost effective production process. Preferably the coloured polymer
particles are simply separated from the reaction composition by
filtration, preferably by pouring the suspension through a pore
size filter, i.e. a 0.1 .mu.m pore size filter. Preferably the
particles may be washed and/or freeze dried. Another major
advantage is that preferably a miniemulsion polymerisation in
aqueous solution can be used. Miniemulsion polymerisation is a well
known polymerisation process wherein barely water soluble monomers
are polymerised by water-soluble initiators. This route gives
excellent control over monodispersity, particle size with a small
diameter range of sub-micron size for image quality. Use of water
as a solvent gives obvious safety and environmental advantages over
use of organic solvents. The selection of the polymerisation
conditions depends on the required size and size distribution of
the particles. Adjustment of polymerization conditions is well
known to someone skilled in the art.
Advantageously, the procedure by which an emulsion polymerisation
is carried out has a profound effect upon the resulting particle
size and polymer properties. Indeed, particles with quite different
performance characteristics can be produced from the same reaction
formulation by appropriate control of polymerisation process and
conditions used. The skilled artisan is familiar with such
polymerisation conditions and knows how to use and control them.
Comprehensive reviews of emulsion polymerisation conditions are
given in "Emulsion polymerization"; van Herk, Alex; Gilbert, Bob;
Department of Polymer Chemistry, Eindhoven University of
Technology, Eindhoven, Neth. Editor(s): Van Herk.
Preferably, a batch emulsion polymerisation process is used wherein
all reactants are completely added at the outset of the
polymerisation process. In such process only relatively few
variables have to be adjusted for a given formulation. Preferred
changes which can be made in such cases are to the reaction
temperature, reactor design and the type and speed of stirring.
Thus, a batch emulsion polymerisation process is used for
manufacture versus a semi-continuous batch process because of
limited versatility and simple evaluations of reaction
formulation.
It is also possible to use a simple 1-step reaction in a
non-aqueous, preferably non-polar medium. The preferred solvents
are non-polar hydrocarbon solvents, especially such used in EPD
fluids, i.e. the Isopar series (Exxon-Mobil), Norpar, Shell-Sol
(Shell), Sol-Trot (Shell), naphtha, and other petroleum solvents,
as well as long chain alkanes such as dodecane, tetradecane, decane
and nonane. Especially preferred is dodecane. Oil-soluble
initiators are preferred in this dispersion polymerisation.
Preferably the coloured polymer particles are simply separated from
the reaction suspension by filtration, preferably by pouring the
suspension through a pore size filter, i.e. a 0.1 .mu.m pore size
filter, or the particles can be cleaned by centrifuging.
A further advantage of the particles made by the present process is
that a surfactant-free emulsion copolymerisation process can be
used. Surfactants are usually key formulation variables in emulsion
polymerisation because of their impact on the intraparticle
stability and particle size control but they may have a detrimental
effect on the electrophoretic response. Since the A-B diblock
copolymer is bound in the particle, it is highly unlikely to leach
into any solvent suitable for EPD.
A main subject of the invention are coloured polymer particles
comprising monomer units of at least one monomer, of at least one
A-B diblock copolymer, of at least one polymerisable dye,
optionally selected from dyes of Formulas 1 to 7, optionally of at
least one charged co-monomer, and optionally of at least one
crosslinking co-monomer.
An essential component of polymer particles prepared by the present
process is an A-B diblock copolymer which acts as steric stabiliser
and/or surface modifier into the particles. Advantageously the A-B
diblock copolymer consists of a hydrophobic A block and a
hydrophilic B block. It is the B block which can be accurately
charged to give additional charge repulsion but also charge to move
the polymer particles to electrodes. That is especially preferred
for EPD applications.
The A block can be prepared from most monomer types, in particular
methyl methacrylate, ethylhexyl methacrylate and styrene.
Preferably, the A block is of similar nature to the polymer in the
particles to ensure incorporation during synthesis, and so that the
A-B diblock copolymer remains entangled in the particle. If the
particle is comprised mainly of polymethylmethacrylate (PMMA), then
the A block should be PMMA, if the particle is comprised mainly of
polystyrene, then the A block should be polystyrene etc. Further
suitable A block polymers are polymers of: 2-ethylhexyl
methacrylate, benzyl methacrylate, butyl methacrylate, cyclohexyl
methacrylate, ethyl methacrylate, hexyl methacrylate, isobutyl
methacrylate, lauryl methacrylate, stearyl methacrylate, phenyl
methacrylate, tert-butyl methacrylate and the acrylate,
methacrylamide, styrenic and acrylamide equivalents.
The B block can be prepared from most monomer types, in particular
chargeable monomers such as dimethylaminoethyl methacrylate and
methacrylic acid. It is preferred that the B block shows the same
charge as charged co-monomers and/or the dyes of the polymer
particles. So, the B block preferably is a hydrophilic unit
comprising e.g. polyacrylic acid which can be made anionic (sodium
salt etc.) when the polymer particles comprise acrylic acid.
Preferred cations are quaternised amine monomers with counter ions
such as chloride or methyl sulfate. Furthermore, the B block
comprises amino groups when the polymer particles comprise amino
groups. Such B blocks can be quaternised to give hydrophilic,
cationic blocks. Preferred anions are carboxylic acid or sulfonic
acid monomers such as methacrylic acid and 3-sulfopropyl
methacrylate.
Especially preferred is poly-N,N'-dimethylaminoethyl methacrylate
(PDMAEMA) as block B. The PDMAEMA block can be accurately
quaternised to give a hydrophilic, cationic block quaternised to
give samples with e. g. 10%, 20% and 100% permanent charge. Such
cationic B blocks fit best to 2-methacryloxy ethyl trimethyl
ammonium chloride (MOTAC), and commonly used water soluble
polymerisable cationic dyes. Further suitable B block polymers are
polymers of: diethylaminoethyl methacrylate, 2-aminoethyl
methacrylate, [3-(methacryloylamino)propyl]dimethylamine, acrylate
and acrylamide equivalents of these and quaternised salts of these
monomers.
Especially preferred are A-B diblock copolymers consisting of PMMA
as block A and PDMAEMA as block B. The PMMA block is consistent
with the preferred latex and the PDMAEMA block sticks out from the
surface causing steric repulsion.
Preferred A-B diblock copolymers according to the invention are
PMMA.sub.m-q.sub.xPDMAEMA.sub.n wherein m is the number of monomer
units of block A, n is the number of monomer units of block B, and
q.sub.x is the percentage of quaternisation of block B based on the
total number of amino groups. n is preferably >10, especially in
the range of 10-20, m is preferably >10, especially in the range
of 15-110 and q.sub.x is preferably >10%, especially 10%, 20%
and 100%. Especially preferred are PMMA.sub.14-PDMAEMA.sub.21,
PMMA.sub.14-q.sub.20PDMAEMA.sub.21,
PMMA.sub.14-q.sub.100PDMAEMA.sub.21, PMMA.sub.14-PDMAEMA.sub.54,
PMMA.sub.14-q.sub.20PDMAEMA.sub.54,
PMMA.sub.14-q.sub.100PDMAEMA.sub.54, PMMA.sub.14-PDMAEMA.sub.108,
PMMA.sub.14-q.sub.20PDMAEMA.sub.108,
PMMA.sub.14-q.sub.100PDMAEMA.sub.108.
A-B diblock copolymers having a molecular weight Mn of 2000-50000,
preferably 3000-30000, especially 4000-25000, are preferred.
Especially A-B diblock copolymers with a narrow molecular weight
distribution polydispersity index (PDI)<1.5, preferably <1.3,
especially <1.1 are preferred. The molecular weight Mn can be
determined by size exclusion chromatography (SEC) in
tetrahydrofuran using PMMA as standard or are calculated based on
results from .sup.1H NMR analyses. Preferably the molecular weight
Mn is determined by size exclusion chromatography (SEC) in
tetrahydrofuran as described in detail in the following
experimental part.
A-B diblock copolymers and their synthesis are known to the skilled
artisan. Block copolymers with a narrow weight distribution are
particularly prepared by living radical polymerisations, such as
atom transfer radical polymerisation (ATRP), nitroxide-mediated
polymerisation (NMP), and reversible addition fragmentation
transfer polymerisation (RAFT). The characteristics of living
polymerisation are polymerisation proceeding until all monomer is
consumed, molecular weight control by stoichiometry of reaction,
and block copolymer preparation by sequential monomer addition.
Preferably A-B diblock copolymers are prepared by RAFT
polymerisation. RAFT polymerisation is a two step synthesis wherein
a homopolymer forming block A is prepared in a first step and
coupled in a second step by use of the RAFT agent with the monomer
constituting the B block. Suitable RAFT agents are known,
especially 4-cyanopentanoic dithiobenzoate (CPDB) is used. RAFT and
the synthesis of RAFT agents have been described in the literature
(J. Chiefari et al, Macromolecules, 1998, 31, 5559; Moad G. et al.,
Polym. Int., 2000, 49, 993-1001; Zard S. Z. et al, Tet. Lett, 1999,
40, 277-280; Thang S. H. et al, Tet. Lett, 1999, 40,
2435-2438).
Preferably, the B block of the A-B diblock copolymer is charged,
e.g. quaternised if it comprises amino groups. Such quaternisation
is preferably done by reaction with methyl halogen, especially
methyl iodide. Reaction conditions are public knowledge.
Advantageously, the invention provides a simple way for synthesis
of polymer particles having steric stability, charge,
mono-dispersity, and colour. Such particles facilitate the
construction of electrophoretic displays utilising the shutter
mode, regarded as one of the main contenders for a subtractive mode
EPD display. Advantages of the A-B diblock copolymer used as steric
stabilisers in process and particles according to the invention may
be, in particular: control of steric stabilisation by
independently, accurately control of the length of the steric
stabiliser by incorporation of an AB block polymer, accurately
control of the length of the chargeable part of the stabiliser
(hydrophilic B block), independently of the particle-like part,
tailor the stabiliser to the particle, e.g. if the particle is made
from PMMA the stabiliser may be partly from PMMA (hydrophobic A
block), control of particle charge by incorporation of a stabiliser
with accurate charge, by using a steric stabiliser which contains
charge or can be charged, the particles are movable in an electric
field.
The monomers (and co-monomers) described in the following for
preparation of the polymeric particles can also be combined with
the polymerisable dyes to produce a polymerisable dye/monomer
mixture and/or the monomers can be incorporated stepwise into the
polymerisable mixture to produce special effects, for example a
core-shell effect so that there is more dye on the shell of the
particles. Particularly preferable are monomers which are similar
to the polymerisable dye, such as methyl methacrylate with Disperse
red 1 acrylate. Addition of a co-monomer seems advantageous in that
it increases the amount of reactive groups available for
polymerisation, the polymerisation proceeds faster with additional
monomer.
The particles can be prepared from most monomer types, in
particular methacrylates, acrylates, methacrylamides,
acrylonitriles, .alpha.-substituted acrylates, styrenes and vinyl
ethers, vinyl esters, propenyl ethers, oxetanes and epoxys but
would typically be prepared from largest percentage to be monomer,
then cross-linker, and include a charged monomer (e.g. quaternised
monomer). Especially preferred are methyl methacrylate and ethylene
glycol dimethyl methacrylate as a cross-linker and 2-methacryloxy
ethyl trimethyl ammonium chloride (MOTAC) as reactive charged
monomer but many others could be used, the following are all
examples of which could be used which are commercially available
from the Sigma-Aldrich chemical company.
Methacrylates:
Methacrylic acid, Methyl methacrylate (MMA), Ethyl methacrylate
(EMA), n-Butyl methacrylate (BMA), 2-Aminoethyl methacrylate
hydrochloride, Allyl methacrylate, Benzyl methacrylate,
2-Butoxyethyl methacrylate, 2-(tert-Butylamino)ethyl methacrylate,
Butyl methacrylate, tert-Butyl methacrylate, Caprolactone
2-(methacryloyloxy)ethyl ester, 3-Chloro-2-hydroxypropyl
methacrylate, Cyclohexyl methacrylate, 2-(Diethylamino)ethyl
methacrylate, Di(ethylene glycol) methyl ether methacrylate,
2-(Dimethylamino)ethyl methacrylate, 2-Ethoxyethyl methacrylate,
Ethylene glycol dicyclopentenyl ether methacrylate, Ethylene glycol
methyl ether methacrylate, Ethylene glycol phenyl ether
methacrylate, 2-Ethylhexyl methacrylate, Furfuryl methacrylate,
Glycidyl methacrylate, Glycosyloxyethyl methacrylate, Hexyl
methacrylate, Hydroxybutyl methacrylate, 2-Hydroxyethyl
methacrylate, 2-Hydroxyethyl methacrylate, Hydroxypropyl
methacrylate Mixture of hydroxypropyl and hydroxyisopropyl
methacrylates, 2-Hydroxypropyl 2-(methacryloyloxy)ethyl phthalate,
Isobornyl methacrylate, Isobutyl methacrylate, 2-Isocyanatoethyl
methacrylate, Isodecyl methacrylate, Lauryl methacrylate,
Methacryloyl chloride, Methacrylic acid, 2-(Methylthio)ethyl
methacrylate, mono-2-(Methacryloyloxy)ethyl maleate,
mono-2-(Methacryloyloxy)ethyl succinate, Pentabromophenyl
methacrylate, Phenyl methacrylate, Phosphoric acid 2-hydroxyethyl
methacrylate ester, Stearyl methacrylate, 3-Sulfopropyl
methacrylate potassium salt, Tetrahydrofurfuryl methacrylate,
3-(Trichlorosilyl)propyl methacrylate, Tridecyl methacrylate,
3-(Trimethoxysilyl)propyl methacrylate, 3,3,5-Trimethylcyclohexyl
methacrylate, Trimethylsilyl methacrylate, Vinyl methacrylate.
Preferably Methyl methacrylate (MMA), Ethyl methacrylate (EMA),
Methacrylic acid, and/or n-Butyl methacrylate (BMA) are used.
Acrylates:
Acrylic acid, 4-Acryloylmorpholine,
[2-(Acryloyloxy)ethyl]trimethylammonium chloride, acrylic acid,
2-(4-Benzoyl-3-hydroxyphenoxy)ethyl acrylate, Benzyl
2-propylacrylate, 2-Butoxyethyl acrylate, Butyl acrylate,
tert-Butyl acrylate, 2-[(Butylamino)carbonyl]oxy]ethyl acrylate,
tert-Butyl 2-bromoacrylate, 4-tert-Butylcyclohexyl acrylate,
2-Carboxyethyl acrylate, 2-Carboxyethyl acrylate oligomers
anhydrous, 2-(Diethylamino)ethyl acrylate, i(ethylene glycol) ethyl
ether acrylate technical grade, Di(ethylene glycol) 2-ethylhexyl
ether acrylate, 2-(Dimethylamino)ethyl acrylate,
3-(Dimethylamino)propyl acrylate, Dipentaerythritol
penta-/hexa-acrylate, 2-Ethoxyethyl acrylate, Ethyl acrylate,
2-Ethylacryloyl chloride, Ethyl 2-(bromomethyl)acrylate, Ethyl
cis-(.beta.-cyano)acrylate, Ethylene glycol dicyclopentenyl ether
acrylate, Ethylene glycol methyl ether acrylate, Ethylene glycol
phenyl ether acrylate, Ethyl 2-ethylacrylate, 2-Ethylhexyl
acrylate, Ethyl 2-propylacrylate, Ethyl
2-(trimethylsilylmethyl)acrylate, Hexyl acrylate, 4-Hydroxybutyl
acrylate, 2-Hydroxyethyl acrylate, 2-Hydroxy-3-phenoxypropyl
acrylate, Hydroxypropyl acrylate, Isobornyl acrylate, Isobutyl
acrylate, Isodecyl acrylate, Isooctyl acrylate, Lauryl acrylate,
Methyl 2-acetamidoacrylate, Methyl acrylate, Methyl
.alpha.-bromoacrylate, Methyl 2-(bromomethyl)acrylate, Methyl
3-hydroxy-2-methylenebutyrate, Octadecyl acrylate, Pentabromobenzyl
acrylate, Pentabromophenyl acrylate, Poly(ethylene glycol) methyl
ether acrylate, Poly(propylene glycol) acrylate, Poly(propylene
glycol) methyl ether acrylate Soybean oil, epoxidized acrylate,
3-Sulfopropyl acrylate potassium salt, Tetrahydrofurfuryl acrylate,
3-(Trimethoxysilyl)propyl acrylate, 3,5,5-Trimethylhexyl acrylate.
Preferably Methyl acrylate, Ethyl acrylate, Acrylic acid, and/or
n-Butyl acrylate are used.
Acrylamides:
2-Acrylamidoglycolic acid, 2-Acrylamido-2-methyl-1-propanesulfonic
acid, 2-Acrylamido-2-methyl-1-propanesulfonic acid sodium salt
solution, (3-Acrylamidopropyl)trimethylammonium chloride solution,
3-Acryloylamino-1-propanol solution purum,
N-(Butoxymethyl)acrylamide, N-tert-Butylacrylamide, Diacetone
acrylamide, N,N-Dimethylacrylamide,
N-[3-(Dimethylamino)propyl]methacrylamide, N-Hydroxyethyl
acrylamide, N-(Hydroxymethyl)acrylamide,
N-(Isobutoxymethyl)acrylamide, N-Isopropylacrylamide,
N-Isopropylmethacrylamide, Methacrylamide, N-Phenylacrylamide,
N-[Tris(hydroxymethyl)methyl]acrylamide.
Styrenes
Styrene, Divinyl benzene, 4-Acetoxystyrene,
4-Benzyloxy-3-methoxystyrene, 2-Bromostyrene, 3-Bromostyrene,
4-Bromostyrene, .alpha.-Bromostyrene, 4-tert-Butoxystyrene,
4-tert-Butylstyrene, 4-Chloro-.alpha.-methylstyrene,
2-Chlorostyrene, 3-Chlorostyrene, 4-Chlorostyrene,
2,6-Dichlorostyrene, 2,6-Difluorostyrene, 1,3-Diisopropenylbenzene,
3,4-Dimethoxystyrene, .alpha.,2-Dimethylstyrene,
2,4-Dimethylstyrene, 2,5-Dimethylstyrene,
N,N-Dimethylvinylbenzylamine, 2,4-Diphenyl-4-methyl-1-pentene,
4-Ethoxystyrene, 2-Fluorostyrene, 3-Fluorostyrene, 4-Fluorostyrene,
2-Isopropenylaniline, 3-Isopropenyl-.alpha.,.alpha.-dimethylbenzyl
isocyanate, Methylstyrene, .alpha.-Methylstyrene, 3-Methylstyrene,
4-Methylstyrene, 3-Nitrostyrene, 2,3,4,5,6-Pentafluorostyrene,
2-(Trifluoromethyl)styrene, 3-(Trifluoromethyl)styrene,
4-(Trifluoromethyl)styrene, 2,4,6-Trimethylstyrene. Preferably
Styrene and/or Divinyl benzene are used.
Vinyl Groups
3-Vinylaniline, 4-Vinylaniline, 4-Vinylanisole, 9-Vinylanthracene,
3-Vinylbenzoic acid, 4-Vinylbenzoic acid, Vinylbenzyl chloride,
4-Vinylbenzyl chloride, (Vinylbenzyl)trimethylammonium chloride,
4-Vinylbiphenyl, 2-Vinylnaphthalene, 2-Vinylnaphthalene, Vinyl
acetate, Vinyl benzoate, Vinyl 4-tert-butylbenzoate, Vinyl
chloroformate, Vinyl chloroformate, Vinyl cinnamate, Vinyl
decanoate, Vinyl neodecanoate, Vinyl neononanoate, Vinyl pivalate,
Vinyl propionate, Vinyl stearate, Vinyl trifluoroacetate.
Other monomers which may be used are those which have groups to
help stabilisation of the particles, e.g. Poly(ethylene glycol)
methyl ether acrylate, Poly(ethylene glycol) phenyl ether acrylate,
lauryl methacrylate, Poly(ethylene glycol) methyl ether acrylate,
Poly(propylene glycol) methyl ether acrylate, Lauryl acrylate and
fluorinated monomers of above. Some of the monomers have groups for
further reaction if so desired, e.g. Glycidyl ethacrylate,
2-Hydroxyethyl methacrylate.
The following compounds can be used as intraparticle crosslinking
monomers for solubility control and solvent swelling resistance:
ethylene glycol dimethacrylate (EGDMA), allyl methacrylate (ALMA),
divinyl benzene, Bis[4-(vinyloxy)butyl] adipate,
Bis[4-(vinyloxy)butyl] 1,6-hexanediylbiscarbamate,
Bis[4-(vinyloxy)butyl] isophthalate, Bis[4-(vinyloxy)butyl]
(methylenedi-4,1-phenylene)biscarbamate, Bis[4-(vinyloxy)butyl]
succinate, Bis[4-(vinyloxy)butyl]terephthalate,
Bis[4-(vinyloxymethyl)cyclohexylmethyl] glutarate, 1,4-Butanediol
divinyl ether, 1,4-Butanediol vinyl ether, Butyl vinyl ether,
tert-Butyl vinyl ether, 2-Chloroethyl vinyl ether,
1,4-Cyclohexanedimethanol divinyl ether, 1,4-Cyclohexanedimethanol
vinyl ether, Di(ethylene glycol) divinyl ether, Di(ethylene glycol)
vinyl ether, Ethylene glycol butyl vinyl ether, Ethylene glycol
vinyl ether, Tris[4-(vinyloxy)butyl] trimellitate,
3-(Acryloyloxy)-2-hydroxypropyl methacrylate,
Bis[2-(methacryloyloxy)ethyl] phosphate, Bisphenol A propoxylate
diacrylate, 1,3-Butanediol diacrylate, 1,4-Butanediol diacrylate,
1,3-Butanediol dimethacrylate, 1,4-Butanediol dimethacrylate,
N,N'-(1,2-Dihydroxyethylene)bisacrylamide, Di(trimethylolpropane)
tetraacrylate, Diurethane dimethacrylate,
N,N'-Ethylenebis(acrylamide), Glycerol 1,3-diglycerolate, Glycerol
dimethacrylate, 1,6-Hexanediol diacrylate, 1,6-Hexanediol
dimethacrylate, 1,6-Hexanediylbis[oxy(2-hydroxy-3,1-propanediyl)]
bisacrylate, Hydroxypivalyl hydroxypivalate
bis[6-(acryloyloxy)hexanoate], Neopentyl glycol diacrylate,
Pentaerythritol diacrylate, Pentaerythritol tetraacrylate,
Pentaerythritol triacrylate, Poly(propylene glycol) diacrylate,
Poly(propylene glycol) dimethacrylate,
1,3,5-Triacryloylhexahydro-1,3,5-triazine,
Tricyclo[5.2.1.0]decanedimethanol diacrylate, Trimethylolpropane
benzoate diacrylate, Trimethylolpropane ethoxylate methyl ether
diacrylate, Trimethylolpropane ethoxylate triacrylate,
Trimethylolpropane triacrylate, Trimethylolpropane trimethacrylate,
Tris[2-(acryloyloxy)ethyl] isocyanurate, Tri(propylene glycol)
diacrylate.
Optionally, the monomer composition comprises at least one charged
co-monomer. Examples of cationic monomers for particle stability
and particle size control are 2-methacryloxy ethyl trimethyl
ammonium chloride (MOTAC), acryloxy ethyl trimethyl ammonium
chloride (AOTAC), [3-(Methacryloylamino)propyl]trimethylammonium
chloride, [2-(Methacryloyloxy)ethyl]trimethylammonium methyl
sulfate solution, tetraallyl ammonium chloride, diallyl dimethyl
ammonium chloride, (Vinylbenzyl)trimethylammonium chloride.
Preferably 2-methacryloxy ethyl trimethyl ammonium chloride
(MOTAC), acryloxy ethyl trimethyl ammonium chloride (AOTAC) and
[2-(Methacryloyloxy)ethyl]trimethylammonium methyl sulfate solution
are used.
Examples of anionic monomers are sodium, potassium or triethylamine
salts of methacrylic acid, Acrylic acid, 2-(Trifluoromethyl)acrylic
acid, 3-(2-Furyl)acrylic acid, 3-(2-Thienyl)acrylic acid,
3-(Phenylthio)acrylic acid, Poly(acrylic acid) potassium salt,
Poly(acrylic acid) sodium salt, Poly(acrylic acid), Poly(acrylic
acid, sodium salt) solution, trans-3-(4-Methoxybenzoyl)acrylic
acid, 2-Methoxycinnamic acid, 3-Indoleacrylic acid,
3-Methoxycinnamic acid, 4-Imidazoleacrylic acid, 4-Methoxycinnamic
acid, Poly(styrene)-block-poly(acrylic acid),
Poly(acrylonitrile-co-butadiene-co-acrylic acid), dicarboxy
terminated, Poly(acrylonitrile-co-butadiene-co-acrylic acid),
dicarboxy terminated, glycidyl methacrylate diester,
2,3-Diphenyl-Acrylic Acid, 2-Me-Acrylic Acid, 3-(1-Naphthyl)Acrylic
Acid, 3-(2,3,5,6-Tetramethylbenzoyl)Acrylic Acid,
3-(4-Methoxyphenyl)Acrylic Acid, 3-(4-Pyridyl)Acrylic Acid,
3-p-Tolyl-Acrylic Acid, 5-Norbornene-2-Acrylic Acid,
Trans-3-(2,5-Dimethylbenzoyl)Acrylic Acid,
Trans-3-(4-Ethoxybenzoyl)Acrylic Acid,
Trans-3-(4-Methoxybenzoyl)Acrylic Acid,
2,2'-(1,3-Phenylene)Bis(3-(2-aminophenyl)Acrylic Acid),
2,2'-(1,3-Phenylene)Bis(3-(2-Aminophenyl)Acrylic Acid)
hydrochloride, 2,2'-(1,3-Phenylene)Bis(3-(2-Nitrophenyl)Acrylic
Acid), 2-[2-(2',4'-Difluoro[1,1'-Biphenyl]-4-Yl)-2-Oxoethyl]Acrylic
Acid, 2-(2-(2-Chloroanilino)-2-Oxoethyl)-3-(4-Methoxyphenyl)Acrylic
Acid,
2-(2-((2-Hydroxyethyl)Amino)-2-Oxoethyl)-3-(4-Methoxyphenyl)Acrylic
Acid, 2-(2-(Cyclohexylamino)-2-Oxoethyl)-3-(4-Methoxyphenyl)Acrylic
Acid.
A preferred monomer composition comprises methyl methacrylate and
ethylene glycol dimethacrylate as a cross-linker and 2-methacryloxy
ethyl trimethyl ammonium chloride (MOTAC) or
[3-(methacryloylamino)propyl]-trimethylammonium chloride as
reactive charged monomer.
Preferably, a water soluble initiator is used in the
surfactant-free emulsion copolymerisation in order to control size,
particle morphology and to reduce the residual monomers at the end
of the reaction. Examples are azo compounds or peroxide compounds,
hydroperoxides or peracid esters. Preferably azo compounds are
used, especially azobis(isobutylamidine) hydrochloride (AIBA) and
similar compounds.
Preferably, an oil soluble initiator is used in the non-aqueous
copolymerisation in order to control size, particle morphology and
to reduce the residual monomers at the end of the reaction.
Preferably an oil-soluble thermal initiator is added in the present
process. Preferably 2,2'-Azobis(2.4-dimethyl valeronitrile),
Dimethyl 2,2'-azobis(2-methylpropionate),
2,2'-Azobis(2-methylbutyronitrile) or Vazo 67 are used.
The present process preferably provides a simple way of preparing
coloured particles by emulsion polymerisation and by a
polymerisation of a polymerisable dye in-situ which does not leach
into typical EPD fluids. Use of a polymerisable dye in the
formative stage of the particle, enables the dye to become
irreversibly bound with the monomers and co-monomers and become an
intrinsic part of the particle. Since the dye is covalently bound
to the monomers in the particle, it is highly unlikely to leach
into any solvent suitable for EPD. Moreover, in this synthesis the
dye and the surface modifiers are separate entities and can be
changed independently unlike in the state of the art in which the
dye and charge are intrinsically linked.
An essential component of this process is a polymerisable dye. In
general the polymerisable dyes may be solvent soluble or water
soluble and they may be anionic, cationic or neutral. Preferably
water soluble dyes are used. The function of the polymerisable dye
is to colour the particle. The polymerisable dye consists of a
chromophore, one or more polymerisable groups, optional linker
groups (spacers), and optional groups to modify physical properties
(like solubility, light fastness, etc.) and optionally charged
group(s).
The polymerisable dye preferably comprises a chromophoric group and
a functional group or plurality of functional groups selected from
polymerisable groups e.g. methacrylates, acrylates,
methacrylamides, acrylamides, acrylonitriles, .alpha.-substituted
acrylates, styrenes and vinyl ethers, vinyl esters, propenyl
ethers, oxetanes and epoxys etc., in particular methacrylates and
acrylates. The polymerised group may be attached directly to the
chromophoric group or may be attached through a linker group. An
example of a suitable linker group is an optionally substituted
alkyl chain, a polyether alkyl chain, a cycloalkyl or aromatic
ring, heteroaromatic ring or a combination thereof.
The chromophoric group preferably comprises of conjugated aromatic
(including heteroaromatic) and/or multiple bonds including: azo
(including monoazo, bisazo, trisazo, linked azos etc), metallised
azo, anthraquinone, pyrroline, phthalocyanine, polymethine,
aryl-carbonium, triphendioxazine, diarylmethane, triarylmethane,
anthraquinone, phthalocyanine, methine, polymethine, indoaniline,
indophenol, stilbene, squarilium, aminoketone, xanthene, fluorone,
acridene, quinolene, thiazole, azine, induline, nigrosine, oxazine,
thiazine, indigoid, quinonioid, quinacridone, lactone,
benzodifuranone, flavonol, chalone, polyene, chroman, nitro,
naphtholactam, formazene or indolene group or a combination of two
or more such groups. Preferred chromophoric groups are azo groups
(especially monoazo, and bisazo), anthraquinone and phthalocyanine
groups. Preferably the polymerisable dye comprises a chromophoric
group and one or more functional groups selected from an acrylate
or methacrylate backbone.
A polymerisable dye may contain a single chromophore, for example
with bright yellow, magenta or cyan colours and self shade blacks.
However, it may also contain mixed covalently attached chromophores
for example to obtain a black colour, by covalently attached brown
and blue or yellow, magenta and cyan. Green can be obtained by
yellow and cyan etc. Extended conjugated chromophores can also be
used to obtain some shades. For example, bis- and trisazo compounds
can be used to obtain blacks and other duller shades (navy blue,
brown, olive green, etc).
Mixtures of polymerisable dyes can also be used to obtain the
correct particle shade; for example a black from single component
mixtures of brown and blue or yellow, magenta and cyan
pre-polymerised dyes. Similarly shades can be tuned for example by
adding small quantities of separate polymerisable dyes to modify
the colour of the particles (e.g. 95% yellow and 5% cyan to get a
greener yellow shade).
Modified polymerisable dyes (with reactive group(s)) from the
application groups of reactive (anionic), direct (anionic), acidic
(anionic) and basic (cationic) dyes as designated by the Colour
Index (published by The Society of Dyers and Colourists with the
American Association of Textile Chemists and Colorists e.g.
3.sup.rd edition 1982) are preferred. Optionally, the dyes may be
selected from dyes of Formulas 1 to 7.
##STR00001## ##STR00002## wherein R1, R2, R3, R5, R7=alkyl,
preferably C1-C4 alkyl, R4, R6, R8=H or CH.sub.3, Hal=halogen, R9,
R10, R12, R13, R15, and R17 to R19=H and alkyl, preferably C1-C4
alkyl, especially CH3 and C2H5, R11, R14, R16, and R20=H or CH3,
preferably CH3, L is a single bond, optionally substituted
cycloalkyl or aromatic ring, linear or branched, optionally
substituted, alkylene, where one or more non-adjacent C atoms may
be replaced by O, S and/or N, and/or one or more double and/or
triple bonds may be present in the chain and/or side chain or a
combination thereof, preferably phenylene or C1-C6 alkyl or a
polyether alkyl chain or a combination thereof, and A-=halogen,
monobasic acid (oxo) anions, preferably acetate, propionate,
lactate, methane sulphonate, p-toluenesulphonate, hydroxide, or
nitrate.
Dyes, especially the preferred dyes, disclosed in WO 2010/089057,
WO 2012/019704, WO 2013/079146, and WO 2013/170935 are advantageous
for the present invention. Preferably dyes with more than one
polymerisable group are used. In principle any polymerisable dye
can be used, preferable with more than one polymerisable group
(most preferably with 2 polymerisable groups) and preferably with a
methacrylate or acrylate function. Additionally, a dye which is
insoluble in non-polar type solvents could be used, for example a
cationic or anionic dye, since this will not preferentially leach
into the organic solvent phase but remain in a particle.
Most preferred dyes and their synthesis are disclosed in WO
2010/089060, WO 2010/089057, WO 2012/019704, WO 2013/170935, and WO
2013/079146.
Examples of polymerisable dyes are summarised in the following
Tables:
TABLE-US-00001 TABLE 1 Examples of Solvent Soluble Reactive Dyes,
Dye Examples 1-8 are commercially available from Sigma-Aldrich
chemical company 1 Disperse red 1 acrylate ##STR00003## 2 Disperse
Red 1 methacrylate ##STR00004## 3 Disperse Red 13 acrylate
##STR00005## 4 Disperse Red 13 methacrylate ##STR00006## 5 Disperse
Yellow 7 methacrylate ##STR00007## 6 Disperse Yellow 7 acrylate
##STR00008## 7 Disperse Orange 3 acrylamide ##STR00009## 8 Disperse
Orange 3 methacrylamide ##STR00010## 9 ##STR00011## 10 ##STR00012##
11 ##STR00013## 12 ##STR00014## 13 ##STR00015## 14 ##STR00016## 15
##STR00017## 16 ##STR00018## 17 ##STR00019## 18 ##STR00020## 19
##STR00021## 20 ##STR00022## 21 ##STR00023## 22 ##STR00024## 23
##STR00025## Magenta 14 ##STR00026##
Cationic polymerisable dyes contain a covalently attached group or
groups which have a positive charge in the application or contain a
positive charge in the chromophore group. They can be derived from
protonation or quaternation of nitrogen, phosphorous, oxygen or
sulphur atoms or groups containing them, for example heteroaromatic
(thiazole, imidazole) delocalised nitrogen bases (guanidine etc).
Associated anions preferably have a single charge and can
preferably be halogen, preferably F.sup.-, Cl.sup.-, Br.sup.-,
monobasic acid (oxo) anions, preferably acetate, propionate,
lactate, methane sulphonate, p-toluenesulphonate, hydroxide,
nitrate).
Preferred examples of water soluble cationic polymerisable dyes are
listed in Table 2 (counter ion MeOSO.sub.3; also preferably
suitable are Cl.sup.-, Br.sup.-, and acetate)
TABLE-US-00002 TABLE 2 1 Basic blue 41 methacrylate ##STR00027## 2
##STR00028## 3 ##STR00029## 4 ##STR00030## 5 Yellow 4 ##STR00031##
6 ##STR00032## 7 ##STR00033## 8 ##STR00034## 9 Magenta 3
##STR00035## 10 Magenta 3 ##STR00036## ##STR00037## 12 ##STR00038##
13 Magenta 4 ##STR00039## 14 Magenta 4 ##STR00040## 15 ##STR00041##
16 ##STR00042##
Anionic polymerisable dyes contain a covalently attached group or
groups which have a negative charge in the application and can be
derived from deprotonation of an acidic group for example
sulphonic, carboxylic, phosphonic acids. Associated cations
preferably have a single charge and can be metallic (Li.sup.+,
Na.sup.+, K.sup.+ etc), charged nitrogen (NH.sub.4.sup.+,
NEt.sub.3H.sup.+, NEt.sub.4.sup.+, NMe.sub.4.sup.+, imidazolium
cation etc), positively charged phosphorous, sulphur etc. Preferred
examples of water soluble anionic dyes are the Na.sup.+,
NH.sub.4.sup.+, NEt.sub.4.sup.+ salts of the acids.
Another preferred example is
CuPc(SO.sub.3.sup.-).sub.n(SO.sub.2NHCH.sub.2CH.sub.2COOCMe=.dbd.CH.sub.2-
)m where CuPc is copper phthalocyanine and m.gtoreq.1, n.gtoreq.1,
m+n.gtoreq.2 and .ltoreq.16 and preferably in the range of 2-5.
Preferred dye acids are listed in Table 3. Preferred water
dispersible neutral dyes are listed in Table 4.
TABLE-US-00003 TABLE 3 1 ##STR00043## 2 ##STR00044## 3
##STR00045##
TABLE-US-00004 TABLE 4 1 ##STR00046## 2 ##STR00047##
Polymerisable water-soluble dye monomers such as the acrylate or
methacrylate derivatives of cationic Basic Blue 41 (listed in Table
2 as numbers 1 and 2) and similar dyes according to Formula 1 can
be used. Such dyes and their preparation are disclosed in WO
2010/089057 and WO 2010/089060.
Also preferred are dyes having a structure like dyes 5-8 of Table 2
or similar dyes as shown in Formula 4.
##STR00048## wherein R9 and R10=independently of one another H and
alkyl, preferably C1-C4 alkyl, especially H, CH.sub.3 and
C.sub.2H.sub.5, R11=H or CH3, preferably CH.sub.3, and and L is a
single bond, optionally substituted cycloalkyl or aromatic ring,
linear or branched, optionally substituted, alkylene, where one or
more non-adjacent C atoms may be replaced by O, S and/or N, and/or
one or more double and/or triple bonds may be present in the chain
and/or side chain or a combination thereof, preferably phenylene or
C1-C6 alkyl,
Especially preferred are compounds of Formula 4 with all R9 being
identical, preferably equal to CH.sub.3 or C.sub.2H.sub.5, R10
equal to CH.sub.3 or C.sub.2H.sub.5 and R11 equal to CH.sub.3, and
L equal to C.sub.2H.sub.4.
The preparation of such polymerisable dyes is exemplified for the
methacrylate derivative with L=C.sub.2H.sub.4, R9=CH.sub.3 and
R10=C.sub.2H.sub.5, which can be prepared by a 3-step reaction as
shown in the following scheme:
##STR00049##
Preparation of Coupling Component
##STR00050##
Also preferred are dyes having a structure like dyes 9-12 of Table
2 or similar dyes as shown in Formula 5 a/b.
##STR00051## wherein L is a single bond, optionally substituted
cycloalkyl or aromatic ring, linear or branched, optionally
substituted, alkylene, where one or more non-adjacent C atoms may
be replaced by O, S and/or N, and/or one or more double and/or
triple bonds may be present in the chain and/or side chain or a
combination thereof, preferably phenylene or C1-C6 alkyl, and R12
and R13=H and alkyl, preferably C1-C4 alkyl, especially CH.sub.3
and C.sub.2H.sub.5, and R14=H or CH.sub.3, preferably CH.sub.3.
Especially preferred are compounds of Formulas 5 with R12 and R13
equal to alkyl, preferably C1-C4 alkyl, especially CH.sub.3 or
C.sub.2H.sub.5, R14 equal to CH.sub.3 and L equal to
C.sub.2H.sub.4.
The preparation of such polymerisable dyes is exemplified for the
methacrylate derivative with L=C.sub.2H.sub.4, R12=CH.sub.3 and
R13=C.sub.2H.sub.5, which can be prepared by a 3-step reaction as
shown in the following scheme:
##STR00052##
Also preferred are dyes having a structure like dyes 13-16 of Table
2 or similar dyes as shown in Formula 6 a/b.
##STR00053## wherein L is a single bond, optionally substituted
cycloalkyl or aromatic ring, linear or branched, optionally
substituted, alkylene, where one or more non-adjacent C atoms may
be replaced by O, S and/or N, and/or one or more double and/or
triple bonds may be present in the chain and/or side chain or a
combination thereof, preferably phenylene or C1-C6 alkyl, R15=H and
alkyl, preferably C1-C4 alkyl, especially CH.sub.3 or
C.sub.2H.sub.5, and R16=H or CH.sub.3, preferably CH.sub.3.
Especially preferred are compounds of Formulas 6 with R15 equal to
CH.sub.3 and C.sub.2H.sub.5, R16 equal to CH.sub.3 and L equal to
C.sub.2H.sub.5.
The preparation of such polymerisable dyes is exemplified for the
methacrylate derivative with R15=C.sub.2H.sub.5 according to
Formula 6b, which can be prepared by a 4-step reaction as shown in
the following scheme:
##STR00054##
Also preferred are dyes having a structure like dye 24 of Table 1
or similar dyes as shown in Formula 7.
##STR00055## wherein L is a single bond, optionally substituted
cycloalkyl or aromatic ring, linear or branched, optionally
substituted, alkylene, where one or more non-adjacent C atoms may
be replaced by O, S and/or N, and/or one or more double and/or
triple bonds may be present in the chain and/or side chain or a
combination thereof, preferably phenylene or C1-C6 alkyl. R17 to
R19 independently of one another equal to H and alkyl, preferably
C1-C4 alkyl, especially CH.sub.3 and C.sub.2H.sub.5, and R20=H or
CH.sub.3, preferably CH.sub.3.
Especially preferred are compounds of Formula 7 with R17 and R18
equal to CH.sub.3 and C.sub.2H.sub.5, R19 equal to H or CH.sub.3,
R20 equal to CH.sub.3 and L equal to C.sub.2H.sub.5.
The preparation of such polymerisable dyes is exemplified for the
methacrylate derivative with R17 and R18=C.sub.2H.sub.5 and R19=H,
which can be prepared by a 3-step reaction as shown in the
following scheme:
##STR00056##
Preferably acrylate or methacrylate derivatives of Disperse red 1,
dyes of Formula 1, especially methacrylate or acrylate derivative
of cationic Basic Blue 41, dyes of Formula 2, especially with R5
and R6=CH.sub.3 and Hal=Cl, and dyes of Formula 3, especially with
R7 and R8=CH.sub.3, dyes of Formula 4, especially with
R9=C.sub.2H.sub.5 and R10 and R11=CH.sub.3, dyes of Formula 5 a/b,
especially with R11 and R13=CH.sub.3 and R12=C.sub.2H.sub.5, dyes
of Formula 6a/b, especially with R15=C.sub.2H.sub.5 and
R16=CH.sub.3, and dyes of Formula 7, especially with R17 and R18
equal to C.sub.2H.sub.5, R19 equal to H, R20 equal to CH.sub.3 and
L equal to C.sub.2H.sub.5 are used as polymerisable dyes for the
invention. Especially preferred are the methacrylate derivative of
cationic Basic Blue 41, and the preferred dyes of Formulas 4, 5, 6,
and 7.
In general, all dyes according to Formulas 1 to 7 can be used in
polymerisable compositions for the preparation of coloured polymer
particles for use in electrophoretic fluids and displays. The dyes
can be used in combination with monomers, co-monomers, optionally
surfactants, optionally stabilisers, and initiators and the
polymerisation method may be emulsion polymerisation or non-aqueous
polymerisation as described in the foregoing.
Preferably dyes with more than one polymerisable group are used. In
principle any polymerisable dye can be used, preferable with more
than one polymerisable group (most preferably with 2 polymerisable
groups) and preferably with a methacrylate or acrylate function.
Additionally, a dye which is insoluble in non-polar type solvents
could be used, for example a cationic or anionic dye, since this
will not preferentially leach into the organic solvent phase but
remain in a particle.
Most preferred dyes and their synthesis are disclosed in WO
2010/089057, WO 2012/019704, WO 2013/170935, and WO
2013/079146.
In a preferred variant of the invention, coloured polymer particles
prepared by emulsion or dispersion polymerisation comprise units of
at least one polymerisable dye, e. g. according to Formulas 1 to 7,
of at least one monomer, optionally of at least one charged
co-monomer, and optionally of at least one crosslinking co-monomer.
Advantageously, such coloured polymer particles comprise
additionally at least one A-B diblock copolymer according to the
present invention.
In another preferred variant of the invention, coloured polymer
particles are prepared by use of polymerisable dyes with at least
two polymerisable groups. Especially, polymerisable dyes according
to WO 2012/019704, WO 2013/170935, and WO 2013/079146 can be
used.
The polymerisable composition of the invention usually comprises up
to 10%, preferably 0.005-7.5%, especially 0.05-5% of A-B diblock
copolymer, up to 10%, preferably 0.005-10%, especially 0.05-5% by
weight of dye, 50-95%, preferably 70-90%, by weight of monomer,
1-40%, preferably 1-10%, by weight of crosslinking monomer, 1-30%,
preferably 1-10%, by weight of ionic monomer and 0.1-10%,
preferably 0.1-5%, by weight of initiator, all percentages are
based on the total weight of the polymerisable composition (except
solvent).
Cross-linked copolymer nanoparticles can preferably be prepared by
emulsifier-free copolymerisation of methyl methacrylate (MMA),
ethylene glycol dimethacrylate (EGDMA),
[3-(methacryloylamino)propyl]-trimethylammonium chloride, and dye
monomer, preferably dyes of Formulas 1-6, especially the preferred
dyes described in the foregoing, using 2,2'-azobis
(2-methylpropionamidine) dihydrochloride as an initiator and a
(PMMA-PDMAEMA) diblock copolymer, especially
(PMMA.sub.14-PDMAEMA.sub.21), (PMMA.sub.14-PDMAEMA.sub.54) or
(PMMA.sub.14-PDMAEMA.sub.108), as steric stabiliser. Preferably
quaternised (PMMA-PDMAEMA) diblock copolymers are used. Preferably,
emulsion polymerisations are conducted using a batch process,
When the polymer particles are prepared without the use of a
polymerisable dye, it is possible to colour the particles by
incorporation of at least one dye by known techniques, such as
solvent swelling of particles as described in WO 2009/100803. A
large number of possibly absorbable dyes are suitable such as azo
dyes, anthraquinone dyes, triarylmethane dyes, acridine dyes,
cyanine dyes, oxazine dyes, polymethine dyes, or thiazine dyes.
Azo-based dyes, anthraquinone-based dyes, and triarylmethane-based
dyes are preferred examples. Suitable dyes are preferably soluble
in the particle swelling solvent and insoluble in water. This
feature allows various dyes to be driven by the solvent within the
nanoparticles and retained inside for. Preferred dyes are Waxoline
blue APFW from Lubrizol (chemical category: anthraquinone), mixture
of solvent yellow (colour index: 11021)+solvent blue (colour index:
61556) distributed by Europhtal-France, organol red distributed by
Europhtal France (chemical category: p. Phenylazoaniline), macrolex
blue RR GRAN from Bayer (chemical category: anthraquinone),
macrolex red violet from Bayer (chemical category: anthraquinone),
solvent yellow 16 (colour index 12700) distributed by Europhtal
France, Waxoline black OBP [solvent yellow 14
(anthraquinone)+carbon black)] from Lubrizol.
Preferably a pre-polymerised dye is used in this colouring
technique. Pre-polymerised means that a polymerisable dye has been
polymerised before it is used to colour a polymer particle.
Pre-polymerised dyes that have been homo-polymerised such as
commercially available Poly(Disperse Red 1 methacrylate) are
suitable, also suitable are pre-polymerised dyes which have been
polymerised with other monomers, e.g. Disperse Yellow 7 acrylate
which has been polymerised together with methyl methacrylate.
Especially preferred is the use of polymerisable dyes which are
polymerised in a subsequent process step. Suitable polymerisable
dyes are those described in the foregoing for co-polymerisation
with monomers and A-B diblock copolymers to form coloured polymer
particles, advantageously the preferred dyes.
In general the dyes for may be solvent soluble or water soluble and
they may be anionic, cationic or neutral. Mixtures of dyes can also
be used to obtain the correct particle shade; for example a black
from single component mixtures of brown and blue or yellow, magenta
and cyan pre-polymerised dyes. Similarly shades can be tuned by for
example by adding small quantities of separate pre-polymerised dyes
to modify the colour of the particles (e.g. 95% yellow and 5% cyan
to get a greener yellow shade). Finally, the polymer particles may
be washed and optionally dried.
Polymer particles prepared according to the invention are
preferably spherical particles with a size (diameter) in the range
of 50-1000 nm and preferably with a monodisperse size distribution.
Preferred particle sizes are 50-600 nm, preferably 50-560 nm,
especially 50-500 nm, even more preferred 100-400 nm. Especially
preferred are particles having a particle size of 150-400 nm,
especially 150-350 nm. Particle sizes are determined by photon
correlation spectroscopy of aqueous particle dispersions by a
common apparatus such as a Malvern NanoZS particle analyser or
preferably by SEM (Scanning Electron Microscopy) and image
analysis.
The size of polymer particles in electrophoretic fluids may be
different from sizes measured in aqueous dispersions because of the
influence of solvents and/or surfactants. In electrophoretic
fluids, the polymer particles of the invention preferably have a
particle size of 100-800 nm, especially 100-700 nm, preferably
150-700 nm are preferred. Especially preferred are polymer
particles having a particle size of 150-600 nm.
Particles of the invention are primarily designed for use in
electrophoretic displays. So, further subjects of the invention are
electrophoretic fluids and electrophoretic displays comprising
particles according to the invention. A typical electrophoretic
display preferably consists of the particles dispersed in a low
polar or non-polar solvent along with additives to improve
electrophoretic properties, such as stability and charge, and
optionally inorganic particles. Examples of such electrophoretic
dispersions are well described in the literature, for example U.S.
Pat. No. 7,247,379; WO 99/10767; US 2007/0128352; U.S. Pat. Nos.
7,236,290; 7,170,670; 7,038,655; 7,277,218; 7,226,550; 7,110,162;
6,956,690; 7,052,766; 6,194,488; 5,783,614; 5,403,518;
5,380,362.
Typical additives to improve the stability of the electrophoretic
fluid (either by steric stabilisation or by use as a charging
agent) are known to experts in the field and include (but are not
limited to) the Brij, Span and Tween series of surfactants
(Aldrich), the Solsperse, Ircosperse and Colorburst series
(Lubrizol), the OLOA charging agents (Chevron Chemicals) and
Aerosol-OT (Aldrich). Any other additives to improve the
electrophoretic properties can be incorporated provided they are
soluble in the formulation medium, in particular thickening agents
or polymer additives designed to minimise settling effects.
The dispersion solvent can be chosen primarily on the basis of
dielectric constant, refractive index, density and viscosity. A
preferred solvent choice would display a low dielectric constant
(<10, more preferably <5), high volume resistivity (about
10.sup.15 ohm-cm), a low viscosity (less than 5 cst), low water
solubility, a high boiling point (>80.degree. C.) and a
refractive index and density similar to that of the particles.
Tweaking these variables can be useful in order to change the
behaviour of the final application. For example, in a
slow-switching application such as poster displays or shelf labels,
it can be advantageous to have an increased viscosity to improve
the lifetime of the image, at the cost of slower switching speeds.
However in an application requiring fast switching, for example
e-books and displays, a lower viscosity will enable faster
switching, at the cost of the lifetime in which the image remains
stable (and hence an increase in power consumption as the display
will need more frequent addressing). The preferred solvents are
often non-polar hydrocarbon solvents such as the Isopar series
(Exxon-Mobil), Norpar, Shell-Sol (Shell), Sol-Trol (Shell),
naphtha, and other petroleum solvents, as well as long chain
alkanes such as dodecane, tetradecane, decane and nonane). These
tend to be low dielectric, low viscosity, and low density solvents.
A density matched particle/solvent mixture will yield much improved
settling/sedimentation characteristics and thus is desirable. For
this reason, often it can be useful to add a halogenated solvent to
enable density matching. Typical examples of such solvents are the
Halocarbon oil series (Halocarbon products), or
tetrachloroethylene, carbon tetrachloride, 1,2,4-trichlorobenzene
and similar solvents. The negative aspect of many of these solvents
is toxicity and environmental friendliness, and so in some cases it
can also be beneficial to add additives to enhance stability to
sedimentation rather than using such solvents. The preferred
additives and solvents used in the formulation of the particles of
the invention are OLOA11000 (Chevron Chemicals), Ircosperse 2153
(Lubrizol Ltd), and dodecane (Sigma Aldrich)
Usually electrophoretic fluids comprise a charged inorganic
nanoparticle such as titania, alumina or barium sulphate, coated
with a surface layer to promote good dispersibility in dielectric
media and a dielectric fluid media. Furthermore, the coloured
particles of the present invention may be used in combination with
white reflective polymer particles prepared by a process comprising
the steps of a) forming a reverse emulsion comprising at least one
polymer, at least one white reflective particle, at least one polar
solvent, at least one non-polar solvent, and at least one
surfactant and b) removing the polar solvent or polar solvents by
evaporative methods. "Reverse emulsion" means that a non-polar
solvent (preferably dodecane, or comparable aliphatic
hydrocarbons)) forms the continuous phase and a polar solvent
(preferably water) forms the discontinuous phase. Such process is
also called either "evaporative precipitation" or "reverse emulsion
solvent removal" (RESR) due to the steps involved in forming a
reverse emulsion and then removing the solvent from the internal
phase by evaporative methods to form a solid particle.
The solvents and additives used to disperse the particles are not
limited to those used within the examples of this invention and
many other solvents and/or dispersants can be used. Lists of
suitable solvents and dispersants for electrophoretic displays can
be found in existing literature, in particular WO 99/10767 and WO
2005/017046 The Electrophoretic fluid is then incorporated into an
Electrophoretic display element by a variety of pixel
architectures, such as can be found in C. M. Lampert, Displays;
2004, 25(5) published by Elsevier B.V., Amsterdam. The
Electrophoretic fluid may be applied by several techniques such as
inkjet printing, slot die spraying, nozzle spraying, and
flexographic printing, or any other contact or contactless printing
or deposition technique.
Electrophoretic displays comprise typically, the electrophoretic
display media in close combination with a monolithic or patterned
backplane electrode structure, suitable for switching the pixels or
patterned elements between the black and white optical states or
their intermediate greyscale states.
The electrophoretic particles according to the present invention
are suitable for all known electrophoretic media and
electrophoretic displays, e.g. flexible displays, TIR-EPD (total
internal reflection electrophoretic devices), one particle systems,
two particle systems, dyed fluids, systems comprising
microcapsules, microcup systems, air gap systems and others as
described in C. M. Lampert, Displays; 2004, 25(5) published by
Elsevier B.V., Amsterdam. Examples of flexible displays are dynamic
keypads, e-paper watches, dynamic pricing and advertising,
e-readers, rollable displays, smart card media, product packaging,
mobile phones, lab tops, display card, digital signage. Particles
of the invention may also be used in optical, electrooptical,
electronic, electrochemical, electrophotographic, electrowetting
displays and/or devices, e.g. TIR (total internal reflection
electronic devices), and in security, cosmetic, decorative, and
diagnostic applications.
The disclosures in the cited references are expressly also part of
the disclosure content of the present application. The following
examples explain the present invention in greater detail without
restricting the scope of protection.
EXAMPLES
Abbreviations
AIBN: 2,2'-azobis(2-methylpropionitrile) or 2, 2'
azoisobutyronitrile
CPDB: 4-cyanopentanoic dithiobenzoate
DMAEMA: N,N'-dimethylaminoethyl methacrylate
MMA: Methyl methacrylate
RAFT: Reversible-Addition Fragmentation Chain-Transfer
DMSO Dimethyl sulfoxide
THF Tetrahydrofuran
PTFE Polytetrafluoroethylene
PMMA Poly(methyl methacrylate)
PDMAEMA Poly(N,N'-dimethylaminoethyl methacrylate)
A-B diblock copolymers PMMA-b-PDMAEMA are prepared by RAFT
polymerisation according to J. Chiefari et al, Macromolecules,
1998, 31, 5559 using CPDB, MMA, DMAEMA, and AIBN.
Description of Analytical Techniques
Particle Analysis
The characterisation of the formulations is performed using a
Malvern NanoZS particle analyser. This instrument measures the size
of particles in dispersion and the zeta potential of an
electrophoretic fluid. The Zeta potential (ZP) is derived from the
real-time measurement of the electrophoretic mobility and thus is
an indicator of the suitability of the fluid for use in
electrophoretic applications. Particle size is also calculated
using SEM and image analysis in some cases. The SEM used is a Leo
1455 VP SEM and the image analysis software used is ImageJ. At
least 500 particles are counted in each case and the particle size
polydispersity is calculated as the percentage standard deviation
of the mean size.
.sup.1H NMR
.sup.1H NMR spectra are recorded on a Bruker AC-500 (500 MHz)
spectrometer using 5 mm diameter tubes. The NMR solvents used are
CDCl.sub.3 or in DMSO. The chemical shift scale is calibrated to
the NMR solvent peak. The analyses of the spectra are carried out
using Bruker 1D WinNMR software. The polymer conversions are
determined by using the peak integral value corresponding to the
vinyl protons of the monomer, and the integral value corresponding
to the broad CH.sub.2 polymer peak plus the equivalent monomer
CH.sub.2 group. The following equation is used:
.times..times..times..times..times..times..times..times..times..times..ti-
mes..times..times..times..times..times..intg..intg..intg.
##EQU00001##
Size Exclusion Chromatography (SEC)
SEC is used to determine the number average molar mass (M.sub.n)
and the polydispersity index (PDI=M.sub.w/M.sub.n with M.sub.w the
weight average molar mass) of the polymers. The polymer samples are
dissolved in THF and filtered through a 0.2 .mu.m PTFE membrane
filter. The samples are injected into two PLgel mixed C columns in
series (bead diameter 5 .mu.m), thermostated at 30.degree. C. The
flow rate of the THF eluent is 1 mL/minute. Detection is made with
a RI detector. Data analysis is performed using the Cirrus software
from Polymer Laboratories, and the calculation made using a
calibration curve based on poly(methyl methacrylate) PMMA standards
from Polymer Laboratories. The following Mark-Houwink parameters
are used for PMMA, K=10.4 and .alpha.=0.697.
Proof of Incorporation of AB Polymers
The AB block polymers are quaternised using methyl iodide to
calculate how much polymer has been included in these particles. An
argentometric titration using a Metrohm 798 MPT Titrino apparatus
with TiST and a silver ring electrode is used. A surface charge
titration with silver nitrate solution 0.1 mol/L (slow) is used to
determine the quantity of AB diblock polymer incorporated in the
particles. About 10.0000 g latex is weighed into a 150 mL beaker,
deionised water (100 ml) and nitric acid (5 ml, 25%) are added and
mixed. A potentiometric titration is performed with silver nitrate
solution (0.1 mol/L) while strongly stirring. The calculation takes
place automatically after the end of titration by means of the
instrument software acc. to the following formula:
.function..times..times..times..times..function..times..times..times..tim-
es..times. ##EQU00002## V(AgNO.sub.3)=consumption of volumetric
AgNO.sub.3 solution 0.1 mol/L t(AgNO.sub.3)=titre of volumetric
AgNO.sub.3 solution 0.1 mol/L sample weight substance=weighed-in
mass of substance
Example 1
[3-{4-Ethyl-2[-(2-methylacrylolyloxy)-ethyl]amino}-phenylazo)phenyl]
trimethylammonium Chloride (Yellow 4)
##STR00057##
Preparation of Coupling Component
##STR00058##
Stage 1. Preparation of 3-Amino-N,N,N-trimethylanilinium
Sulphate
Dimethyl sulphate (50.45 g., 0.4 mol) is added dropwise to a
stirred solution of 3-aminoacetanilide (15 g, 0.1 mol) in water
(100 ml) at 50.degree. C. at 50-60.degree. C. pH is maintained at
7.5-8.5 with sodium hydroxide solution. The mixture is stirred for
16 hours at 50.degree. C. after which a solution is formed. The
solution is cooled to 5.degree. C., sulphuric acid (specific
gravity 1.83, 15 ml) is added and the mixture is heated to
100.degree. C. and kept at this temperature for 3 hours. After
cooling, the solution is made up to 150 ml and used as such, that
is 0.01 m/15 ml.
Stage 2. N-Ethyl-N-(2-methacryloyloxyethyl)aniline
Methacryloyl anhydride (18.5 g, 0.12 mol) is added dropwise to a
stirred solution of N-ethyl-N-(2-hydroxyethyl)-aniline (16.5 g, 0.1
mol) in pyridine. The mixture is stirred at 55.degree. C. for 2
hours, poured onto ice/water and extracted with hexane. The organic
layer is passed through silica gel eluted with hexane, followed by
removal of solvent to yield
N-ethyl-N-(2-methacryloyloxyethyl)aniline (17.4 g, 70%), as a pale
yellow oil.
Stage 3.
[3-{4-Ethyl-2[-(2-methylacrylolyloxy)-ethyl]amino}-phenylazo)phen-
yl] trimethylammonium Chloride (Yellow 4)
3-Amino trimethylanilinium sulphate solution (0.01 mol) is
diazotised at 0-5.degree. C.; a solution of 2-methacrylic
acid-(2-ethylphenylamino)-ethyl ester (1.2 g, 0.005 m) in acetic
acid (5 ml) is added. The pH of the cold solution is raised to 3 by
dropwise addition of 2N aqueous ammonia. The mixture is stirred for
16 hours at room temperature to yield a sticky tar which is
dissolved in methylene chloride and purified by passing through
silica gel. Collection of the appropriate fractions followed by
evaporation of the solvent affords a reddish yellow tar (0.19 g,
9%). .lamda. max 432, .epsilon. max 30,000.
Example 2
2-Methacrylic
Acid-2-[ethyl-(5-phenylimino-5H-benzo[a]phenoxazin-9-yl)-amino]-ethyl
Ester (Magenta 4)
##STR00059##
Stage 1. 2-[Ethyl(4-nitrosophenyl)amino]ethanol
2N Sodium nitrite is added dropwise to a stirred solution of
N-ethyl-N-.beta.-hydroxyethyl (16.5 g, 0.1 mol) in dilute
hydrochloric acid, keeping the temperature below 5.degree. C. and
the pH at 1.5 to 2.0, until all of the starting material is
consumed. Ammonia solution is added until the pH 9 is reached and
the resulting oil is extracted with methylene chloride. Removal of
solvent affords a greenish oil. Yield 16 g, 82%.
Stage 2. 9-[Ethyl-(2-hydroxyethyl)-amino]benzo[a]phenoxazin-7-ylium
Nitrate
2-[Ethyl(4-nitrosophenyl)amino]ethanol hydrochloride (4.6 g, 0.02
mol) is made by adding gaseous HCl to a solution of
2-[ethyl(4-nitrosophenyl)amino]ethanol (0.02 mol) in diethyl ether.
The solvent is decanted off and the freshly prepared compound is
added portionwise, over 2 hours to a mixture of 2-naphthol (2.88 g,
0.02 mol) and zinc chloride (1.54 g, 0.0113 mol) in refluxing
methylated spirit (20 ml); refluxing is continued for a further 2
hours. On cooling, solid is collected and washed with a small
volume of methylated spirit (4.5 g, 46%). This solid is stirred in
boiling water (400 ml) and, on cooling, this is treated with conc.
nitric acid (12 ml). The resulting tarry solid is washed by
decantation with dilute nitric acid (0.2 N) and dried. Yield 2.3 g,
29%.
Stage 3.
9-[Ethyl-(2-hydroxyethyl)-amino]-5-phenylamino-benzo[a]phenoxazin-
e
9-[Ethyl-(2-hydroxyethyl)amino]benzo[a]phenoxazin-7-ylium nitrate
(2.3 g, 0.006 mol) and aniline (2.0 g, 0.0215 mol) are stirred in
methanol (25 ml) at room temperature for 16 hours. Solvent is
removed by decantation and the remaining tarry solid is washed
repeatedly by decantation with toluene. After standing the tar
became solid. Yield 2.4 g., 85%.
.lamda..sub.max (MeOH+1 drop 2N HCl) 652 nm; .epsilon..sub.max
60,000.
.lamda..sub.max (acetone) 522 nm, .epsilon..sub.max 35,000;
.lamda..sub.max (acetone+1 drop 2N HCl), .lamda..sub.max 658 nm;
.epsilon..sub.max 70,000.
Stage 4. 2-Methacrylic
acid-2-[ethyl-(5-phenylimino-5H-benzo[a]phenoxazin-9-yl)-amino]-ethyl
Ester (Magenta 4)
Methacryloyl chloride (0.58 g, 0.0057 mol) is added dropwise to a
stirred solution of
9-[ethyl-(2-hydroxyethyl)-amino]-5-phenylamino-benzo[a]phenoxazine
base (1.8 g, 0.0038 mol) in pyridine (15 ml) and the stirred
mixture is maintained at 70.degree. C. for 18 hours. On cooling the
solution is poured into water (150 ml); the resulting solid is
collected, washed thoroughly with water and dried. Yield 1.3 g,
62%.
Example 3
3/4-Methyl-2-[4-{N-ethyl-N-(.beta.-acryloyloxyethyl)phenylamino}phenylazo]-
-[1,2,4]-thiadiazolium Methosulphate (Magenta 3)
##STR00060##
Stage 1. N-Ethyl-N-.beta.-acryloyloxyethyl Aniline
N-Hydroxyethyl-N-ethyl aniline is acylated in quantitative yield by
stirring with methacrylic anhydride in pyridine, for 18 hours at
ambient temperature. A small quantity of water is added to destroy
excess anhydride and the reaction mixture is poured into water. The
product is extracted into hexane and the organic layer passed
through silica gel. On removal of solvent, product is obtained as a
pale yellow oil which is used direct.
Stage 2.
2-[4-{N-ethyl-N-(.beta.-acryloyloxyethyl)phenylamino}phenylazo]-[-
1,2,4]-thiadiazole
2-Amino-1,2,4-thiadiazole (2.02 g, 0.02 mol) is diazotised by
stirring in a mixture of acetic acid and water and adding conc.
sulphuric acid (2 g) followed by sodium nitrite (1.4 g, 0.021 mol).
The mixture is stirred at 0 to 5.degree. C. for 3 hours and excess
nitrous acid is destroyed by adding a small quantity of sulphamic
acid. The above coupling component
N-ethyl-N-.beta.-acryloyloxyethyl aniline (4.66 g, 0.02 mol),
dissolved a small volume of acetic acid is added, with stirring.
The product precipitates as a mobile tar and is extracted with
methylene chloride. This is washed with 2N sodium carbonate
solution and passed through silica gel to remove baseline
impurities. The fractions containing product are collected and
solvent removed to leave a tarry oil which, although essentially
homogeneous by thin layer chromatography, could not be induced to
crystallize.
3/4-Methyl-2-[4-{N-ethyl-N-(.beta.-acryloyloxyethyl)phenylamino}phenylazo]-
-[1,2,4]-thiadiazolium Methosulphate (Magenta 3)
The above disperse dye is dissolved in a mixture of ethyl acetate
and dimethyl sulphoxide. Dimethyl sulphate (1.5 m equiv.) is added
and the stirred mixture is immersed in an oil bath heated to
80.degree. C. The reaction cannot be induced to go to completion so
the reaction mixture is allowed to cool. The precipitated tarry
residue is collected and passed through silica gel. Elution with
ethyl acetate removes starting disperse dye; further elution with
acetone yielded the desired product as a mixture of isomers. Yield
0.2 g, .about.2%.
.lamda..sub.max (methanol) 568 nm
Example 4
Preparation of Methacrylate Ester Derivative of CI Basic Blue 41
(Blue 1)
##STR00061##
Stage 1
2-Amino-6-methoxybenzothiazole (18.0 g) is stirred in a mixture of
acetic acid (70 ml) and propionic acid (50 ml) at 50.degree. C. The
resulting solution is cooled to -10.degree. C. Nitrosylsulphuric
acid solution (40 weight-% in sulphuric acid) (32.0 g) is added
dropwise. This mixture is added to a stirred solution of
N-ethyl-N-(2-hydroxyethyl) aniline and sulphamic acid (1.0 g) in
acetic acid (25 ml) and ice/water (100 ml). After 20 minutes, the
pH is raised to 4 by the dropwise addition of potassium hydroxide
solution. A tarry residue is formed; the mixture is stirred for a
further 2 hours until the tar solidifies. This solid is collected,
washed with water and then dissolved in alcohol and acetone to give
a deep red solution. Hot water is added to precipitate a solid
which is removed by filtration. The solid is washed with cold
alcohol and dried (29.5 g, 83% yield) Mp 178-179.degree. C.
Stage 2
The above hydroxyethyl disperse dye (10.7 g) dye is stirred in
methylene chloride (100 ml) and pyridine (20 ml). Methacrylic
anhydride (10 ml) is added and the mixture is heated under reflux
for 24 hours. On cooling to room temperature, water (5 ml) is added
and the mixture is stirred for 2 hours. A volatile material is
removed under reduced pressure, to leave a tarry residue which is
stirred in 5 weight-% aqueous sodium bicarbonate solution for 16
hours. The resulting crude product is dissolved in methylene
chloride/hexane (60/40) and passed through silica gel. After
removal of solvent the solid residue (9.7 g) is crystallised from
propan-2-ol to yield a rubine crystalline solid.
Yield 7.0 g, 55%. mp 123-125.degree. C.
Stage 3
Dimethyl sulphate (1 ml) is added dropwise to a stirred solution of
the methacrylate ester (1.06 g) in toluene (25 ml) at 100.degree.
C. After 10 minutes a tar begins to deposit on the walls of the
flask and the mixture is allowed to cool to room temperature. The
tar is washed with cold toluene and is stirred overnight in ethyl
acetate (25 ml). The resulting semi-solid residue is collected,
added to propan-2-ol and the mixture is heated to boiling. On
cooling a solid is deposited which is washed with cold propan-2-ol
and dried. Yield 1.22 g, 89%. Mp 140-142.degree. C. (97.3% main
component by hplc) C23H27N4OS gives a mass ion of 439.
A mass spectrum of the sample gave a spectrum in positive ion mode.
(EI+) The spectra show ions at m/z 439 which corresponds with the
cation for the proposed structure.
Example 5
N-[5-Diethylamino-2-(5-ethylthio-[1,3,4]-thiadiazol-2-ylazo)-phe-
nyl]-acrylamide (Magenta 14)
Prepared by a 4 step procedure as detailed below:
##STR00062##
Step 1: N,N-Diethyl-m-phenylene Diamine
3-Diethylaminoacetanilide (10.8 g, 0.05 mol) is stirred under
reflux for 4 hours in 10% HCl (45 ml). The solution is evaporated
to dryness and the tarry residue washed with several portions of
cold acetone until it solidifies. The hydrochloride is dissolved in
water (100 ml) and stirred at 15.degree. C. while caustic liquor is
added dropwise until the pH is 9-10 and the product separates as a
syrup. This product is extracted into methylene chloride, dried
(MgSO.sub.4), poured through silica gel and evaporated to dryness,
yielding N,N-Diethyl-m-phenylene diamine as a mobile, light-brown
oil (9.0 g, approx. 100%).
Step 2: 3-Chloro-N-(3-diethylaminophenyl)-propionamide
N,N-Diethyl-m-phenylene diamine (8.2 g, 0.05 mol) and sodium
hydrogen carbonate (10 g, 0.119 mol) are stirred at room
temperature in methylene chloride (80 ml) while
.beta.-chloropropionyl chloride (7.61 g, 0.06 mol) is added
dropwise over 30 minutes. The reaction mixture is stirred overnight
at room temperature. Water (5 ml) is added and stirred a further 2
hours at ambient temperature. The methylene chloride fraction is
dried (MgSO.sub.4), poured through silica gel and evaporated to
dryness yielding 3-chloro-N-(3-diethylaminophenyl)-propionamide as
a grey-brown solid (12.2 g, 95%). The material is recrystallised
from methanol, isolating the material at 0.degree. C. as almost
colourless needles, mp=88-90.degree. C.
Step 3:
3-Chloro-N-[5-diethylamino-2-(5-ethylthio-[1,2,4]-thiadiazolyl-2-y-
lazo)-phenyl]-propionamide
2-Amino-5-ethylthio-[1,3,4]-thiadiazole (2.32 g, 0.02 mol) is added
in portions to a mixture of propionic acid (10 ml) and acetic acid
(20 ml) and stirred at room temperature. The resultant solution is
cooled and stirred at 0-5.degree. C. while nitrosyl sulphuric acid
(6.34 g, 0.02 mol) is added dropwise. After a further hour at
0-5.degree. C., the diazonium salt solution is added dropwise to a
suspension prepared by adding a solution of
3-chloro-N-(3-diethylaminophenyl)-propionamide (5.5 g, 0.016 mol)
in acetone to a stirred mixture of ice and water containing a
little sulphamic acid. The reaction mixture is stirred overnight,
allowing to warm up to room temperature and the product is
collected by filtration, washed with cold water. After drying, the
crude product is purified by silica flash chromatography and
recrystallisation from methylene chloride/methylated spirits yields
3-chloro-N-[5-diethylamino-2-(5-ethylthio-[1,2,4]-thiadiazolyl-2-ylazo)-p-
henyl]-propionamide as crimson needles (2.5 g, 29%),
.lamda..sub.max (EtOAc) 516 nm, .epsilon..sub.max 60,000, 1/2 band
width 79 nm. The preparation is repeated on 0.015M scale, yielding
2.7 g (42%) of product.
Step 4:
N-[5-Diethylamino-2-(5-ethylthio-[1,3,4]-thiadiazol-2-ylazo)-pheny-
l]-acrylamide (Magenta 14)
3-Chloro-N-[5-diethylamino-2-(5-ethylthio-[1,2,4]-thiadiazolyl-2-ylazo)-p-
henyl]-propionamide (6.1 g, 0.0143 mol) is stirred in
dichloromethane (60 ml) at ambient temperature and triethylamine
(3.1 g, 0.308 mol) are added drop wise. The solution is stirred
overnight, extracted with water (75 ml), dried (MgSO.sub.4) and
evaporated to dryness. Recrystallisation from methylene
chloride/methylated spirit yields
N-[5-diethylamino-2-(5-ethylthio-[1,3,4]-thiadiazol-2-ylazo)-phenyl]-acry-
lamide (Magenta 14) as crimson needles (5.1 g, 91%),
.lamda..sub.max (EtOAc) 518 nm, .epsilon..sub.max 59,000, 1/2 band
width 78 nm.
Example 6
Synthesis of PMMA Particles
A-B diblock copolymer (PMMA.sub.14-PDMAEMA.sub.21) (0.14 g) is
added to water (85 g) in a 250 ml 3 neck flask equipped with a
condenser, an overhead stirrer and a nitrogen inlet. Methyl
methacrylate (7.13 g), ethylene glycol dimethacrylate (0.60 g) and
[3-(methacryloylamino)propyl]trimethylammonium chloride solution
(75 weight % in water) (0.30 g) are added. The reaction mixture is
heated to 70.degree. C. under a nitrogen atmosphere. Initiator
2,2'-azobis (2-methylpropionamidine) dihydrochloride (0.08 g) is
added to water (10 g), stirred until dissolved and added to the
reaction mixture. After 20 hours the latex is allowed to cool to
room temperature, and is filtered through a 5 micron cloth. After
washing with water, zeta-size analysis is 216 nm, zeta-potential is
63 mV in water. The suspension is freeze dried to give a fine white
powder.
PMMA particles are prepared using PMMA-b-PDMAEMA A-B diblock
copolymers 1-9 of Table 5. Details are given in Table 6.
TABLE-US-00005 TABLE 5 Description of diblock copolymers
PMMA-b-PDMAEMA Degree of quaternisa- Mn Sample Polymer tion.sup.a
(g/mol) PDI 1 PMMA.sub.14-PDMAEMA.sub.21 0% 5720.sup.b; 1.14
4770.sup.c 2 PMMA.sub.14-q.sub.20PDMAEMA.sub.21 20% 4830.sup.c 3
PMMA.sub.14-q.sub.100PDMAEMA.sub.21 100% 5070.sup.c 4
PMMA.sub.14-PDMAEMA.sub.54 0% 10735.sup.b; 1.2 10110.sup.c 5
PMMA.sub.14-q.sub.20PDMAEMA.sub.54 20% 10280.sup.c 6
PMMA.sub.14-q.sub.100PDMAEMA.sub.54 100% 10920.sup.c 7
PMMA.sub.14-PDMAEMA.sub.108 0% 18200.sup.b; 1.2 18600.sup.c 8
PMMA.sub.14-q.sub.20PDMAEMA.sub.108 20% 18930.sup.c 9
PMMA.sub.14-q.sub.100PDMAEMA.sub.108 100% 20220.sup.c .sup.athe
degree of quaternisation is calculated from the .sup.1H NMR
analyses in DMSO. .sup.bthe molecular weight Mn and the
polydispersity PDI of sample 1, 4 and 7 are determined by size
exclusion cnromatography (SEC) in tetrahydrofuran using PMMA as
standard. .sup.cMolecular weight are calculated based on results
from .sup.1H NMR analyses.
TABLE-US-00006 TABLE 6 Details of PMMA particles Quantity Dye PMMA
(wt % cf Zeta (wt % cf Particles Additive MMA) MOTAC (g) Potential
Size MMA) PDI 1 Sample 1 2 0.3 62 204 0 2 Sample 1 5 0.3 63 401 0 3
Sample 2 5 0.3 57 187 0 4 Sample 3 5 0.3 64 108 0 5 Sample 4 2 0.3
65 177 0 6 Sample 4 2 0.3 55 206 Blue 1 0.06 example 4 0.5 7 Sample
4 5 0.3 57 115 0 8 Sample 4 5 0 46 84 0 9 Sample 5 0.5 0.3 62 387 0
10 Sample 5 1 0.3 61 262 0 11 Sample 5 2 0.3 56 195 0 12 Sample 5 4
0.3 57 125 0 13 Sample 5 5 0.3 58 138 0 14 Sample 6 2 0.3 62 184 0
15 Sample 6 2 0.3 59 133 Blue 1 0.13 example 4 0.5 16 Sample 6 2
0.3 54 147 Yellow 4 0.09 example 1 0.5 17 Sample 6 5 0.3 60 102 0
18 Sample 6 5 0 54 74 0 19 Sample 6 2 0.3 Magenta 4 example 2 0.5
20 Sample 6 2 0.3 Magenta 3 example 3 0.5 21 Sample 6 2 0 Magenta 3
example 3 0.5 22 Sample 7 2 0.3 61 258 0 23 Sample 7 5 0.3 57 187 0
24 Sample 8 5 0.3 54 111.7 0 25 Sample 9 5 0.3 63 109 0
Proof of Incorporation of AB Polymers:
PMMA Particles 4:
0.71 mmol/100 g Iodide, 2.21 mmol/100 g Chloride (sample weight
13.7 g, 9.4 wt %)
Analysis shows iodide content to be 0.71 mmol per 100 g, compared
to 1.08 mmol per 100 g theory added to reaction mixture, thus
showing 66% incorporation.
PMMA Particles 24:
0.35 mmol/100 g Iodide 1.97 mmol/100 g Chloride (sample weight 11.3
g, 8.3 wt %)
Analysis showed iodide content to be 0.35 mmol per 100 g solution,
compared to 0.357 mmol per 100 g theory showing 98% incorporation
assuming no halide exchange.
Example 7
Electrophoretic Fluid Containing PMMA Particles 22
0.19950 g of PMMA particles 22 is added to 0.0199 g of OLOA 11000
(Chevron Chemicals) and 0.0600 g of Solsperse 3000 (Lubrizol) in
2.002 g of dodecane (Sigma Aldrich) and vortex mixed. The resultant
dispersion is then homogenised using an ultra-turrax T25
homogeniser for 30 minutes and sonicated for a further 30 minutes
in an Ultrawave ultrasonic bath. The dispersion is then roller
mixed overnight to yield an electrophoretic fluid. Size (142 nm),
Electrophoretic Mobility (0.05643 .mu.mcm/Vs), ZP (+60.8 mV)
Example 8
Electrophoretic Fluid Containing PMMA Particles 22
0.0602 g of PMMA particles 22 is added to 0.111 g of Solsperse 3000
(Lubrizol) in 2.08 g of dodecane (Sigma Aldrich) and vortex mixed.
The resultant dispersion is then homogenised using an ultra-turrax
T25 homogeniser for 30 minutes and sonicated for a further 30
minutes in an Ultrawave ultrasonic bath. 0.09 g of Aerosol-OT
(Aldrich) is added as a charge control agent. The dispersion is
then roller mixed overnight to yield an electrophoretic fluid.
Size (172 nm), Electrophoretic Mobility (0.02103 .mu.mcm/Vs), ZP
(-22.7 mV).
Example 9
Electrophoretic Fluid Containing PMMA Particles 1
0.035 g of PMMA particles 1 is added to 0.0102 g of Solsperse 13940
(Lubrizol) in 0.963 g of dodecane (Sigma Aldrich) and vortex mixed.
The resultant dispersion is then homogenised using an ultra-turrax
T25 homogeniser for 30 minutes and sonicated for a further 30
minutes in an Ultrawave ultrasonic bath. The dispersion is then
roller mixed overnight to yield an electrophoretic fluid.)
Size (215 nm), Electrophoretic Mobility (0.01515 .mu.mcm/Vs), ZP
(+16.3 mV)
* * * * *